In recent years, shaped articles of thermosetting resin and composite materials using matrices of thermosetting resin have been finding extensive applications in the general industrial field and the electric field because they exhibit highly desirable dimensional stability, heat resistance, mechanical properties, chemical resistance, and weather proofing properties.
Such molded articles of thermosetting resins have low toughness and impact resistance due to the low elongation and brittleness of the resin. Thus, improvement in these properties have been desired.
In order to improve the toughness and impact resistance of molded articles of thermosetting resins, a rubber component, plastic resin component or a filler have been incorporated into the thermosetting resins.
In the case of incorporation of the rubber component into the thermosetting resin, however, since the rubber component impairs the heat resistance and mechanical properties of the molded article in spite of its ability to improve the toughness and impact resistance of the molded article, the amount of the rubber component is limited. In some applications, it is incorporated into the thermosetting resin only in a low ratio and consequently has an insufficient effect in improving the desired properties. When the thermosetting resin is mixed with a thermoplastic resin, the thermoplastic resin is added to the thermosetting resin as fine powder, or the thermoplastic resin is dissolved in a solvent and subsequently the thermosetting resin is added to the resultant solution (mixture). When the thermoplastic resin is added to a thermosetting resin in a finely divided form, the produced composition lacks homogeneity, and tends to degrade the mechanical properties of the molded article obtained therefrom. When the mixing is effected with the aid of a solvent, the method has the disadvantage that the removal of the solvent from the produced composition is required; the procedure for the production of the composition is troublesome; and the solvent remaining in the produced composition in a minute amount impairs, for example, the heat resistance of the molded article.